Exploration Gateway Platform hosting Reusable Lunar Lander proposed

In a potential marriage of the Space Launch System (SLS) with a central exploration plan, a Boeing-authored presentation has proposed an Exploration Gateway Platform architecture that not only returns man to the lunar surface – via the use of only one SLS launch to a reusable Lunar Lander – but provides a baseline for pathfinders towards an eventual crewed mission to Mars.

Using a Global Exploration Roadmap, the approach utilizes “Near term focus on guiding capabilities, technologies and leveraging ISS,” prior to expanding to “Long term focus (on) Discovery Driven – and Enhanced by – Emerging Technologies”.

While such talk has been heard before, during the continued lack of an exploration roadmap that can provide any real definition, the presentation makes the jump towards a mission goal which has seen its stock raised over recent months, one which involves the crewed return to the Lunar Surface, as the opening prime exploration mission for NASA.

Central to the plan is a deep space platform, known as a gateway, located at Earth-Moon Lagrange (EML) point 1 or 2, after being built from pre-launched hardware, providing the host station for a reusable Lunar Lander – which would also be launched by the SLS Heavy Lift Launch Vehicle (HLV).

Such a concept was previously overviewed in August, showing how the existing hardware would be launched to the ISS – using Atlas launch vehicles in the example cited – prior to full assembly using ISS assets such as the Space Station Remote Manipulator System (SSRMS).

Once constructed, a space tug – powered either by solar electric or chemical – would be utilized to raise the platform to the EML point. Such a proposal claims to be ready for the arrival of crewed missions via the SLS by 2022 – as much as any timeline would be based on the readiness and evolvability of the SLS.

“A Gateway at EML1 or EML2 allows re-usability of the lunar lander which saves money and enhances development of the ultra-reliable systems needed for Mars,” noted the November presentation.

“Our concept lander is much smaller than Altair; Dry mass of 7t, wet mass of 15t (Altair was ~45t wet). The propulsion system is designed to be re-fuelable LOX/Methane.”

HLV capabilities for higher energy missions beyond LEO were examined. This required the use of upper stages. Existing stages from Delta IV and Atlas V and new stage designs using RL-10B2 (existing), RL-60 and J-2X LOX/LH2 rocket engines (as now chosen) were used to estimate payloads to Geosynchronous Transfer Orbit, Geosynchronous Orbit, Trans-Lunar Injection and to the Earth-Moon L1 point,” the presentation noted.

This use of EML-1 related to the launch of a single HLV, carrying a depot to be refuelled using commercial vehicles, reducing the mass required to launch from Earth’s surface on a Lunar or deep space mission via “dry” – and potentially reusable – landers.

“A propellant depot at the Earth-Moon L1 point would significantly improve lunar and deep space exploration mission operations by providing an infrastructure capability for deep space transportation and by opening up participation to international partners and commercial vehicles. This propellant depot outside of Earth gravity well would act as a refuelling station for spacecraft on the way to the lunar surface or Mars,” added the presentation.

Such a plan would result in SLS with an EDS (Earth Departure Stage) delivering Orion and a dry lunar lander to L1. The dry lunar lander would be loaded with 25mt of propellants at the depot to complete the lunar phase of its mission. Dry launch of the LSAM element to L1 would dramatically reduce the spacecraft weight constraints, permitting more flexible and robust operational capabilities to be designed into the lander.

In fact, the first customer to arrive at the platform would likely be the dry lander, while the gateway station was still located at the ISS, prior to the entire stack being sent into deep space via a tug.

“Commissioning crew flies with the lander to the platform,” added the presentation. “Flight test program in the vicinity of the ISS-EP is used to prepare the lander for it’s first landing.”

Once all the hardware is in place at EML-1, the presentation claims there is potential for a single SLS to carry out a full lunar surface mission, as much as the key will be on the evolution of the SLS’ third stage.

In essence, the potential scenario calls for: The launch of the station/gateway platform to Earth-Moon L1 or L2, via a space tug, following assembly at the ISS. Potentially the launch of a reusable LOX/methane lander to the L1/2 Gateway – as much as it’s likely the lander would be sent to the gateway whilst it was still at the ISS. The Launch of the SLS with an Orion and a modified Delta Cryogenic Second Stage (DCSS) to the Gateway.

The scenario then calls for the use first burn of DCSS to stop at Gateway and dock, where it would transfer LOX and methane from DCSS to lander – with the methane stored in an extra tank in-between LOX and LH2. The mission would then be initiated, with a lunar landing using the DCSS to inject to the Moon, with around three DCSS burns being utilized.

The crew would then return to Gateway Platform in the lander, transfer themselves over to the berthed Orion, and return to Earth with a burn from Orion’s SM. It should be noted that all of the key elements would likely be refined prior to a complete plan, as noted in the presentations operational considerations.

However, one of the key benefits of this approach is noted as the saving of potentially billions of dollars to carry out such recurring missions, while “unique science opportunities at L1 Deep-space human exploration analogs exist at L1. (Provides) support for deep-space human exploration missions.”

“The goal for recurring operations should be to deliver the crew and all fuel for the lander in a single SLS launch,” added the presentation.

“The SLS third stage acts as the descent stage for the lander and performs the lunar orbit injection burn as well as most of the lunar descent burn. This allows for the most efficient use of propellant because the high energy LOX/LH2 third stage is used immediately after it gets to L2 and long term storage of LH2 is not required,

Other benefits of a gateway platform are also cited in the overview, such as the potential for telerobotic control of hardware on the lunar surface, the launching of lunar habs to the Moon’s surface, and further references to using this baseline to ramp up towards Mars missions.

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